how to use indexes for both dimensions in multidimensional array

Answer 1

Multidimensional arrays are like matrix(2 dimensions), then the library of matrix(3), library of libraries of matrix(4) and so on.
So indexes(if they are numerics) are like this(It's example of 2 dimensional array with 3 columns, 2 rows):
[0, 0], [0, 1], [0, 2]
[1, 0], [1, 1], [1, 2]

Answer 2

For two dimensional array it should be written like [0][0], [0][1] etc.